A study was made of cerebral blood flow (CBF) in gerbils by Laser doppler velocimetry (LDV). Each animal was subjected to five minute bilateral carotid occlusions each hour for 3 hours. Continuous measurement of CBF was made of the parietal cortex through the cranium. There was excellent consistency and repeatability from gerbil to gerbil. The essential features were: The CBF as revealed by LDV, dropped to zero during ischemia, arose upon release of ischemia to a value slightly above the pre- ischemic value, then declined to a much lower value over the hour before the next occlusion. There was no evidence of an accumulative effect with respect to the ischemia.